Studies by electron spin resonance of radicals produced in the photolysis of alkyl peroxides and hydroperoxides

Abstract

Ultra-violet photolysis of degassed, purified t-butyl peroxide or of its solutions in hydrocarbons, in no case yielded concentrations of radicals detectable by electron spin resonance. In commercial samples of t-butyl peroxide or in t-butyl peroxide containing t-butyl hydroperoxide, large radical concentrations were obtained by photolysis, while in solutions of t-butyl peroxide in pentane, iso-pentane, hexane, heptane or methyl cyclohexane, containing dissolved oxygen or air, radicals were readily detected below 253°K. In aromatic solvents, except in cumene, only low radical concentrations were observed in any circumstances. Photolysis of t-butyl hydroperoxide yielded high radical concentration as did photolysis of its solutions in aliphatic solvents either in the presence or absence of oxygen. In aromatic solvents no radicals were observed unless oxygen was present.

These results can be interpreted on the assumption that the radicals responsible for the e.s.r. signals are either t-butyl peroxy radicals or, for some oxygen-saturated solutions a peroxy radical, derived from the solvent. Attempts to obtain the t-butyl-oxy radical by photolysis of t-butyl peroxide adsorbed on silica gel at low temperatures yielded only methyl radicals and a radical believed to be CH₃˙ CO ˙ CH₂·.